The train that caused the deadly Lac-Megantic disaster was carrying cargo that's considered as flammable as gasoline even though it was labelled as something less volatile, the Transportation Safety Board said Wednesday.

Tankers carrying crude oil derailed and exploded in the Quebec town last July, killing 47 people and levelling the town centre.

Lab tests conducted by the agency confirmed its earlier finding that the hazard level of the material in the tank cars "was not accurately documented," by the Montreal, Maine & Atlantic Railway.

Samples taken from nine of the cars that didn't derail showed the oil's properties were "consistent with those of a light sweet crude oil, with volatility comparable to that of a condensate or gasoline product," the TSB said.

The agency issued safety advisory letters in September urging rail authorities in Canada and the U.S. to review the way they transport dangerous goods and to ensure they are labelled accurately.